Fluids based on fluorocarbon compounds are largely used in vapor-compression heat-transfer systems, in particular air conditioning, heat pump, refrigeration and freezing devices. These devices have in common the fact that they are based on a thermodynamic cycle comprising the vaporization of the fluid at low pressure (in which the fluid absorbs heat); the compression of the vaporized fluid up to a high pressure; the condensation of the vaporized fluid to liquid at high pressure (in which the fluid releases heat); and the expansion of the fluid in order to complete the cycle.
The choice of a heat-transfer fluid (which may be a pure compound or a mixture of compounds) is dictated, on the one hand, by the thermodynamic properties of the fluid, and on the other hand, by additional constraints. Thus, one particularly important criterion is that of the impact of the fluid under consideration on the environment. In particular, chlorinated compounds (chlorofluorocarbons and hydrochlorofluorocarbons) have the disadvantage of damaging the ozone layer. Henceforth, generally non-chlorinated compounds such as hydrofluorocarbons, fluoroethers and fluoroolefins are therefore preferred to them.
It is, however, necessary to develop other heat-transfer fluids that have a global warming potential (GWP) lower than that of the heat-transfer fluids currently used, and that have equivalent or improved performance levels.
Document WO 2007/053697 describes fluoroolefin-based compositions in various uses, and in particular as heat-transfer fluids. The document mentions 1,1,1,4,4,4-hexafluorobut-2-ene.
Document WO 2008/134061 describes azeotropic or azeotrope-like compositions comprising (Z)-1,1,1,4,4,4-hexafluorobut-2-ene in combination with methyl formate, pentane, 2-methylbutane, 1,1,1,3,3-pentafluorobutane, trans-1,2-dichloroethylene or 1,1,1,3,3-pentafluoropropane.
Document WO 2008/154612 describes azeotropic or azeotrope-like compositions comprising (E)-1,1,1,4,4,4-hexafluorobut-2-ene in combination with methyl formate, n-pentane, 2-methylbutane, trans-1,2-dichloroethylene, 1,1,1,3,3-pentafluoropropane, n-butane or isobutane.
Document WO 2010/055146 describes fluoroolefins and the process for producing them. The document mentions in particular (E)-1,1,1,4,4,4-hexafluorobut-2-ene.
Document WO 2010/100254 describes tetrafluorobutenes, optionally as a mixture with hexafluorobutenes, and the use thereof in various applications, including heat transfer.
However, there is still a need to develop other heat-transfer fluids which have a relatively low GWP and which are capable of replacing the usual heat-transfer fluids.
In particular, it is desirable to develop other heat-transfer fluids with a low GWP which are azeotrope-like and/or which exhibit good energy performance levels compared with usual heat-transfer fluids (such as isobutane) and/or improved energy performance levels compared with the known heat-transfer fluids with a low GWP (such as 1,3,3,3-tetrafluoropropene).